1. Field of the Invention
The present invention relates to a wireless communication method of communication time adjustment in Bluetooth devices, and more particularly, to a wireless communication method of a wireless communication device for performing one-to-multi Bluetooth communication by adjusting a time period for a communication between a master device and slave devices when the master device intends to communicate with the slave devices. The present application is based on Korean Patent Application No. 2002-51520, filed Aug. 25, 2001, which is incorporated herein by reference.
2. Description of the Related Art
The Bluetooth technology enables transmission of information such as text data, voice data and video data at a maximum speed of 1 Mbps within a distance range of 10-100 m.
Bluetooth devices, which can communicate with one another through the Bluetooth communication method, construct a communication connection through processes like inquiry scan, page, page scan, etc. During these processes, master and slave devices are determined according to functions thereof.
In order to construct a new connection with another Bluetooth device, each Bluetooth device has to adjust its operational clock and frequency pattern with each other. And among the processes for constructing a new connection among the Bluetooth devices, the inquiry process is that the master device repeatedly sends out its operational frequencies to the slave devices in order to have the slave devices adjust their frequency patterns to the master device.
The inquiry scan is performed by the slave devices, in which the slave devices detect the received frequencies and synchronize to the detected frequencies. The page is the process in which the master device sends out a clock signal so that the slave devices can adjust to the operational clock of the master. In the page scan, the slave devices detect the received clock and synchronize to it. Through these processes, a connection called a ‘piconet’ is constructed, having more than one slave device connected to the master device.
According to the currently suggested Bluetooth communication method, one master device can connect to up to seven slave devices in an active state, for bilateral communication. Further, in order to connect a new slave device to the piconet, the master device first disconnects one of seven active slave devices from the piconet and then connects the new slave device to the piconet in an active state.
According to the Bluetooth communication method, the master and slave devices operate in several modes, i.e., in an active mode in which the master device communicates with the slave devices on a regular basis, and hold, sniff and park modes for power saving. Usually, the hold mode is used when there is no need to send data in a relatively long period of time. In sniff mode, the master and slave devices transmit and receive data only for a predetermined period of time. During the park mode, the slave device periodically communicates with the master device in order to ask for maintenance of synchronization with the master device and shift to the active mode.
The slave device, which operates in one of the hold, sniff and park modes, repeatedly operates in its communication mode according to a predetermined cycle. Although the slave device operating in hold mode actually operates one time, since the slave device in hold mode wakes up at a predetermined time to communicate with the master device, it is considered that the slave device in hold mode also operates periodically like slave devices in other modes.
When all the connected slave devices shift their modes, the master device determines communication time of the respective slave devices through communication and negotiation with the slave devices. Accordingly, through the negotiation with the master device, all the connected slave devices are set to operate according to a predetermined periodical cycle. That is, according to the conventional communication method, the master and slave devices communicate for a time and according to a cycle that are fixed by mutual negotiations among the master and slave devices until the slave devices shift their modes.
Here, the operational cycles of each slave device in each mode can vary according to the negotiation with the master device. Accordingly, although the slave devices begin communication with the master device at different times and according to different cycles in the one-to-multi communication of the Bluetooth communication, different communication of the respective slave devices sometimes causes coincidental overlap of communication of a plurality of slave devices within a certain period of time. And the slave devices communicating with the master device simultaneously may cause interference in the communication with the master device. Accordingly, due to the communication interference among the slave devices, the slave devices can be disconnected from the master device.